Journal of Environmental Biology

Phenotypic and biochemical characterization of root nodule bacteria naturally associated with woody tree legumes in Saudi Arabia

Thobayet Safar Alshaharani¹ and Nader Desouky Shetta^1,2*

¹Range and Forestry Applied Research Unit, Plant Production Department, Food and Agriculture College,

King Saud University, Riyadh 11451, Saudi Arabia

²Forestry and Wood Technology Department, Faculty of Agriculture, Alexandria University, Alexandria 21545, Egypt

*Corresponding Author E-mail: n.shetta@yahoo.com 

Publication Data

Paper received:

30 October 2013

Revised received:

21 January 2014

Accepted:

28 April 2014

Abstract

Thirty root-nodulating bacteria isolates were obtained from the roots of Acacia ampliceps (Maslin), A. ehrenbergiana (Hayne.), A. saligna (Labill.), A. seyal (Del.), A. tortilis (Forssk.), A. tortilis subsp. raddiana (Savi.), Leucaena leucocephala (Lam.) and Vicia faba (L.) trees growing in the Riyadh region. The isolates' phenotypic and biochemical properties were characterized by assessing colony appearance, growth rate, resistance to antibiotics and heavy metals, and tolerance to salinity, elevated temperature and pH. All isolates had same colony morphology and grew on yeast extract mannitol and tryptone yeast agar, but not MGS media. The results also revealed considerable diversity among the isolates, which exhibited different patterns of resistance to abiotic stresses. Most isolates tolerated temperatures up to 37?C and could grow from pH 5.5?8.5 and at a high NaCl concentration (2% w/v). The majority of isolates could utilize a variety of carbohydrates. Most of the isolates displayed resistance to antibiotics in the 75 ?g ml^-1 range, with ~100 ?g ml^-1 the maximum concentration at which growth was observed. All isolates were sensitive to aluminum and resistant to other heavy metals tested, and they were able to reduce nitrate and hydrolyze urea. ? 

 Key words

Legume trees, Phenotypes, Rhizobium isolates 

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